The present invention relates to the field of computerized storage management and in particular to improving the efficiency, consistency, and predictability of file access in a tiered storage architecture.
In such a tiered environment, virtual or physical storage components may be organized into tiers as a function of each component's performance characteristics. Such tiering may be performed for a variety of reasons, such as to reduce requirements for pricier higher-speed storage devices, to better balance workloads, or to more effectively match a class of storage devices with criticality or access frequency of a type of data stored on that class of device.
In some cases, a request to access data that has been migrated from a higher storage tier to a lower storage tier may take significantly longer to fulfill than it would have taken prior to the migration. Such a degradation in storage performance may produce unacceptable response times. For example, a user that has previously enjoyed quick response when accessing a higher-tier storage device may not find response times of a lower-tier device to be acceptable. Even greater user dissatisfaction may occur when longer access times result from a user's attempt to perform multiple concurrent data-access operations from the same lower-tier storage medium or device.
Current methods of managing migration of data between tiers focus on objective parameters that may be measured by means of known technology, such as response times. They do not account for subjective criteria, such as user satisfaction, which may be a complex or subtle function of multiple factors, such as a class of a requested data item, a class of user or other user characteristic, a location or type of facility of the user, an intended application of the requested data, or even a time of day.